Hydraulic brake systems are employed in a variety of towed vehicles including recreation and utility trailers. Conventional hydraulic braking systems in towed vehicles employ a surge brake. The surge brake has a hydraulic piston that controls the flow of hydraulic fluid to the towed vehicle brakes in response to relative motion between the trailer and the towing vehicle. The surge brake is typically mounted on the tongue of the towed vehicle and applies a braking pressure based on the pressure exerted between the towed vehicle and the towing vehicle.
It is generally desirable to control the braking forces that are applied to the towing vehicle and the towed vehicle to reduce disproportionate loads on the respective brake systems. Differences in braking force between the towed vehicle and the towing vehicle can result in significant problems. If the towed vehicle brake pressure is too great, then the towed vehicle will tend to drag the pulling vehicle to a stop upon application of the brakes. Alternatively, if the towing vehicle braking force is greater, the trailer will tend to over run the towing vehicle.
Therefore, the need exists for a braking system that can be controlled from within the towing vehicle to provide an appropriate braking force. A need also exists for a towed vehicle braking system that can be readily adjusted in response to varying road conditions. The need also exists for a braking system that does not require substantial valving, assembly and maintenance.